curl/docs/cmdline-opts/parallel-immediate.md

c	SPDX-License-Identifier	Long	Help	Added	Category	Multi	Scope	See-also	Example
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.	curl	parallel-immediate	Do not wait for multiplexing (with --parallel)	7.68.0	connection curl	boolean	global	parallel parallel-max	--parallel-immediate -Z $URL -o file1 $URL -o file2

--parallel-immediate

When doing parallel transfers, this option instructs curl to prefer opening up more connections in parallel at once rather than waiting to see if new transfers can be added as multiplexed streams on another connection.

By default, without this option set, curl prefers to wait a little and multiplex new transfers over existing connections. It keeps the number of connections low at the expense of risking a slightly slower transfer startup.